November 30, 2005

Scientists Question Age of Ancient Footprints

LONDON (Reuters) - Scientists cast doubt on Wednesday on the age of footprints discovered in Mexico which suggested humans had arrived in the Americas 30,000 years earlier than previously thought.

The fossilised footprints discovered two years ago in volcanic ash near Puebla, Mexico were thought to be 40,000 years old, but researchers in the United States and Mexico who visited the site and collected samples came to a different conclusion.

"You're really only left with two possibilities," said Paul Renne of the University of California, Berkeley.

"One is that they are really old hominids -- shockingly old -- or they're not footprints," he added in a statement.

In 2003, an international team of scientists headed by Silvia Gonzalez of John Moores University in Liverpool, England found about 250 human and animal prints in a layer of volcanic ash.

They estimated that early hunters walked across the ash deposited near a lake 40,000 years ago. Prior to that discovery, humans were thought to have arrived in the Americas across a land bridge from Asia about 11,000 years ago.

But Renne and a team of geologists and anthropologists who used an argon dating technique and another method to analyse the age of fossils said they were about 1.3 million years old.

"We conclude that either hominid migration into the Americas occurred very much earlier than previously believed, or that the features in question were not made by humans on recently erupted ash," Rene and his team said in a report in the journal Nature.